The following is a timeline of the COVID-19 pandemic in the United Kingdom from January 2021 to June 2021.

There are significant differences in the legislation and the reporting between the countries of the UK: England, Scotland, Northern Ireland, and Wales. The numbers of cases and deaths are reported on a government Web site updated daily during the pandemic. The UK-wide COVID Symptom Study based on surveys of four million participants, endorsed by authorities in Scotland and Wales, run by health science company ZOE, and analysed by King's College London researchers, publishes daily estimates of the number of new and total current COVID-19 infections (excluding care homes) in UK regions, without restriction to only laboratory-confirmed cases.

Events January 2021 1 January New Year celebrations are quieter than normal because of COVID restrictions, but several instances of police breaking up illegal parties are reported all around the UK. They include a party at a 500-year-old church in Essex in which the building is damaged by revellers. The R number, the rate at which the virus is transmitted, is estimated to be between 1.1 and 1.3, but a study from Imperial College London suggests the new COVID strain may have actually increased the R number by between 0.4 and 0.7. Saffron Cordery, of NHS Providers, the body that represents hospital trusts, warns the next few weeks will be "nail-bitingly difficult" for the NHS, with staff absences because of the new variant of COVID. A further 53,285 COVID cases are recorded, along with 613 deaths.

2 January As a further 57,725 COVID cases are recorded in the UK, the largest daily number so far, senior doctor Professor Andrew Goddard warns that hospitals across the UK could face the same level of pressure seen in London and the South East in recent days. Batches of the Oxford–AstraZeneca COVID-19 vaccine begin to arrive at hospitals throughout the UK in preparation for vaccination to begin on Monday 4 January. Fiona Godlee, an editor of The BMJ, has asked The New York Times to correct an article that claimed health officials in the UK will allow people to receive doses of two different COVID vaccines, describing the story as one that is "seriously misleading and requires urgent correction". BBC News reports that a number of healthcare workers have criticised the process involved in becoming verified to administer the vaccine, which include answering questions on whether they are trained in how to prevent radicalisation.

3 January A further 54,990 COVID-19 cases are recorded, the sixth day the daily figure has exceeded 50,000. Hospitalized COVID patients reaches 26,626, with 24,316 patients in general beds; COVID represents 30% of NHS hospital capacity.de Quetteville, Harry. (15 January 2021). "UK hospitals have been relatively empty compared to Europe – so why is the NHS struggling?". The Telegraph website Retrieved 16 January 2021. On the eve of the rollout of the Oxford–AstraZeneca COVID-19 vaccine, Prime Minister Boris Johnson says that he expects "tens of millions" of COVID-19 vaccinations to be given over the coming three months; 530,000 doses of the vaccine are ready at hospitals and GPs surgeries to be administered. Boots and Tesco have offered to help with the rollout of COVID-19 vaccinations. Jo Stevens, the Shadow Secretary of State for Digital, Culture, Media and Sport and MP for Cardiff Central, is reported to be in hospital where she is receiving treatment for COVID-19.

4 January Brian Pinker, 82, becomes the first person in the country to receive the Oxford–AstraZeneca COVID-19 vaccine as vaccinations using the vaccine begin in the UK. Margaret Ferrier, the MP for Rutherglen and Hamilton West, is arrested by Scottish police and charged in connection with "alleged culpable and reckless conduct" for using public transport while experiencing COVID symptoms. Prime Minister Boris Johnson later confirms that England will enter a third lockdown from 5 January, with similar restrictions to the first lockdown in March 2020, including school closures to all pupils except from children of keyworkers and vulnerable children. Another lockdown is announced in England and Scotland. The UK's chief medical officers recommend the COVID alert level is moved from level four to level five.

5 January A further 60,916 new COVID-19 cases are confirmed, the largest daily number so far. The UK government says that 1.3 million people in the UK have so far received their first dose of a COVID-19 vaccine. Johnson also promises to provide daily updates on the number of vaccinations administered. Chancellor Rishi Sunak announces that businesses affected by the new lockdown will receive grants of up to £9,000 per property. GPs have been told to "stand down" routine patient care in favour of COVID vaccination in order to ensure the NHS can deliver 14 million vaccines by February. The BBC announces that programming for schools will air on BBC Two and CBBC, as well as online, during lockdown, starting from Monday 11 January. YouTube bans Talkradio for allegedly violating its rules by posting information that contradicts expert advice about the COVID-19 pandemic, but reinstates the station within hours. With England and Scotland back in lockdown, personal trainer Joe Wicks confirms his plans to restart free online PE lessons on Mondays, Wednesdays and Fridays, starting from 11 January. A few days later, musician Bez of Happy Mondays also subsequently announces plans to launch an online fitness class, from 17 January. England's Chief Medical officer, Professor Chris Whitty, suggests "a few" COVID restrictions may be required in Winter 2021–22 to control the virus, particularly if people do not adhere to the government's "stay at home" message.

6 January A further 62,322 new COVID-19 cases are confirmed, the largest daily number so far, a further 1,041 people have died, the largest daily number since April. The number of people in hospital with COVID also tops 30,000, with 30,074 patients being treated. COVID hospital admissions reach 3,967, and begin to decline after this date. Fast food retailer McDonald's announces it will pause its walk-in takeaway service during lockdown. Annemarie Plas, founder of Clap for Our Carers, announces the weekly event will return from the following day, but under the name Clap for Heroes. Fraudsters are sending out fake text messages about the COVID-19 pandemic in an attempt to get hold of people's bank details, it is reported.

7 January NHS trials of two anti-inflammatory drugs, tocilizumab and sarilumab, have indicated they can cut the number of COVID deaths by a quarter. The revived Clap for Heroes initiative is met with a quieter response than its previous run in spring 2020, with founder Annemarie Plas distancing herself from it after receiving online abuse. National Express announces the suspension of its entire coach fleet from midnight on 10 January. The UK government announces that road haulage drivers crossing the English Channel will continue to need a recent negative COVID test until further notice. Prime Minister Boris Johnson announces that the armed forces are to help with the rollout of COVID vaccines, while 1,000 GP surgeries will be able to administer "hundreds of thousands" of vaccines per day by 15 January. 1.5 million vaccine doses have been given so far.

8 January The Moderna vaccine becomes the third COVID vaccine to be given approval for use in the UK. Sadiq Khan, the Mayor of London, declares a "major incident" in London, where he says COVID is "out of control". Research from the COVID Symptom Study suggests COVID cases increased by a third in the UK and reached 70,000 new cases a day between 26 December and 3 January, while the Office for National Statistics estimates 1.2 million people had COVID over the same time period. The R number is estimated to be between 1.0 and 1.4. The UK records its largest number of daily COVID-related deaths so far, with 1,325 new deaths, bringing the total to 79,833. The figure surpasses 21 April 2020, when there were 1.224 deaths. However, average deaths are estimated to be two thirds of the peak in April, suggesting the high daily total may have occurred as a result of a backlog in reporting deaths over the Christmas period. An England-wide advertising campaign launches on television, fronted by Chief Medical Officer Chris Whitty, urging people to stay at home and act as though they have COVID.

9 January A further 1,035 COVID-related deaths take the total past 80,000 to 80,868. People travelling from the UK to the Republic of Ireland must produce a negative COVID test before being allowed to enter that country. With the exception of British and Irish nationals, travellers from Namibia, Zimbabwe, Angola, Botswana, Mauritius and Seychelles, are banned from entering England because of the South Africa COVID strain. Buckingham Palace confirms that Queen Elizabeth and Prince Philip have received COVID vaccinations, which were administered by a royal doctor at Windsor Castle. The Hacking Trust, a property investment company, has approached staff at GP surgeries offering to pay £5,000 for unused COVID vaccines. A spokesman for the Institute of General Practice Management describes the story as "just appalling".

10 January Professor Peter Horby, chair of the government's New and Emerging Respiratory Virus Threats Advisory Group tells the Andrew Marr Show "we are now in the eye of the storm" and "it was bad in March, it's much worse now." Health Secretary Matt Hancock tells the BBC that everybody in the top four most vulnerable groups will be offered a vaccine by 15 February, while every adult in the UK will be offered one by the autumn. Hancock also says that the NHS is under "very serious pressure" and warns people that "flexing the rules" could be fatal. As the National Police Chiefs' Council issues guidelines telling police officers to issue fines more quickly for breaches of COVID regulations, Home Secretary Priti Patel defends the way police have handled lockdown breaches, and says they "will not hesitate" to enforce the rules. Jeremy Brown, Professor of Respiratory Infection at University College London and a member of the Joint Committee on Vaccines and Immunisation, has suggested children may have to stay in isolation until they have been vaccinated. Online retailer Ocado warns customers of possible shortages because of the pandemic, with the possibility of "an increase of missing items and substitutions over the next few weeks".

11 January Sir Simon Stevens, the chief executive of NHS England, has described online videos reported to show empty hospitals as "a lie". The videos, which Stevens says are mostly filmed by people walking through empty hospital corridors, have been used to argue claims the NHS is being overwhelmed by the pandemic are an exaggeration. Professor Chris Whitty, England's Chief Medical Officer, says that the UK will go through the "most dangerous time" in the weeks before the deployment of COVID vaccines begin to have an impact. Health Secretary Matt Hancock confirms that 2.3 million people have now received a COVID vaccine. Chancellor Rishi Sunak warns the economy will "get worse before it gets better". Figures released by the British Retail Consortium indicate that retailers experienced their worst year of sales in 2020, with sales down by 0.3% as a result of the COVID-19 pandemic. Supermarket retailers Morrisons and Sainsbury's announce their intention to prevent customers who refuse to wear face coverings from entering their premises; Sainsbury's will also challenge people who shop in groups. Eye health charity Fight for Sight warns of the damage too much screentime during lockdown could cause to people's eyesight.

12 January The United Arab Emirates is removed from the UK's quarantine exemption list, requiring anyone travelling from there to self-isolate for ten days.